Washing process for the removal of chrome soaps from chrome-tanned furs



Unite States Patent 2 989 362 WASHING PROCESS FdR THE REMOVAL OF gHROlWE SOAPS FROM CHROME-TANNED Rudi Heyden and Jiirgen Plapper, Dusseldorf, Germany, assignors to Bohme Fettchemie G.m.b.H., Dusseldorf, Germany, a corporation of Germany No Drawing. Filed Aug. 2, 1955, Ser. No. 526,067 Claims priority, application Germany Aug. 13, 1954 5 Claims. (Cl. 8-94.14)

This invention relates to a process for removing chrome soaps from chrome-tanned fur skins using chrome complex-active, water-soluble or water-emulsifiable compounds as the washing agents.

It is well known in the leather industry that when animal fur skins containing a relatively large amount of natural fats, for example sheep Skins, are only incompletely degreased prior to the customary chrome-tanning procedure, the natural fats remaining in the fur combine with the chrome-tanning agent and form highly undesirable chrome soap deposits on the fur. These deposits are very diflicult to remove by a simple washing process, and in most cases can be only incompletely removed even by repeatedly washing the fur skins. If the chrome soap deposits are allowed to remain on the fur, they tend to discolor the fur and impart a greenish hue thereto, which substantially reduces the value of such furs on the open market.

It is an object of the present invention to provide a process which permits the complete removal of chrome soaps from chrome-tanned animal furs.

Another object of the present invention is to provide a process for the complete removal of chrome soaps from chrome-tanned animal furs, which can be applied to such furs without substantial additional expense and in conjunction with the customary procedures incident to the production of finished furs.

Other objects and advantages of the invention will be come apparent as the description thereof proceeds.

We have found that the chrome soap deposits formed during the chrome-tannage of incompletely degreased animal furs canbe very readily and completely removed by a treatment of the chrome-tanned furs with an aqueous solution containing water-soluble or water-dispersible compounds which comprise complex-active atom groups, i.e., atom groups which are capable of binding chromium ions by the formation of complex ions. This procedure is most advantageously applied to the chrome-tanned furs subsequent to and immediately after the tanning step, but before drying the furs.

The removal of the insoluble chrome soap deposits may, for example, be accomplished by contacting the furs with aqueous solutions of compounds which contain, in addition to complex-active groups, such as carboxyl groups, oxy groups or phosphoric acid groups, also highmolecular lipophilic radicals with from about 10 to 18 carbon atoms, and Water-solubilizing radicals, such as sulfuric acid ester groups, sulfonic acid groups, polyalkylene oxide groups and the like, in the molecule.

More specifically, compounds suitable for the purpose of the present invention are, for example, Water-soluble monoesters formed by esterifying dior polybasic inorganic or organic acids, such as phosphoric acid, tartaric acid, citric acid, and the like, with high-molecular aliphatic, cycloaliphatic or fatty-aromatic hydroxyl compounds, particularly with fatty alcohols having from about 10 to 18 carbon atoms in the carbon chain, or their sodium or ammonium salts.

Further compounds suitable for the removal of chrome soap deposits from furs in accordance with the present invention are Water-soluble monoesters formed by esterifying polybasic inorganic or organic acids with highfatty alcohols, which contain about 10 to 18 carbon atoms in the carbon chain and which have been alkoxylated with about 5 to 10 mols, preferably 8 mols, of ethylene oxide, for example.

These esters and ester salts form very highly soluble chromium complexes and are therefore highly effective in removing chrome soap deposits from chrome-tanned animal furs.

However, other types of compounds are also very elfective as dissolving agents for chrome soap deposits. For example, the polycarboxylic acids formed by a reaction of unsaturated fatty acids, such as oleic acid, linseed oil fatty acid, soybean oil fatty acid, and the like, with maleic acid, their salts and derivatives, such as their ethoxylation or sulfonation products, for example, may also be effectively used provided these compounds contain at least one and preferably several carboxyl groups capable of forming chromium complexes.

Still further, known chromium complex-forming compounds, such as polyphosphates, polycarboxylic acids of the type of alkylene diarnino-diacetic acid or 'nitrilotriacetic acid or their salts, may be used with advantage for the removal of chrome soaps from animal furs according to the process of the present invention.

The water-soluble monoesters of the alkoxylated highmolecular hydroxyl compounds are most effective when they contain lipophilic radicals, particularly alkyl radicals of medium molecular size. Most suitable of these are mixtures of fatty alcohols having from 12 to 18, but principally from 16 to 18, carbon atoms in the carbon chain. In addition to the esters of high-molecular fatty alcohols, the corresponding esters of cycloaliphatic alcohols, such as naphthenic alcohols, fatty aromatic hydroxyl compounds, for example, alkyl phenols with from 10 to 18 carbon atoms in the alkyl radicals, and the like, may also be used.

The application of the complex-active compounds to the chrome-tanned furs is most suitably combined with a washing step employing the commercial fur-washing agents customarily used, particularly in those cases where the complex-active compounds themselves do not possess surface-active characteristics.

Depending upon the amount of soil in the furs, the washing solution may contain from 0.6 to 3 gm. per liter of the above compounds. Simultaneously, the washing solution may contain from 0.2 to 1 gm. per liter, preferably 0.5 gm. per liter of a commercially available, neutral fur washing agent. The temperature of this washing solution may range from 40 to 50 C. Subsequent to this washing treatment for the removal of chrome soaps from the furs, the pelts may, if desired, be subjected to a further washing treatment at from 40 to 50 C. with a separate solution containing about 1 to 3 gm. per liter of a commercially available, neutral for washing agent. Such a solution may, in addition to other compounds, contain alkyl sulfates, alkyl sulfonates, or alkyl benzene sulfonates.

The following example will further illustrate the present invention and enable others skilled in the art to I understand the invention more completely. It is understood, however, that our invention is not limited to this example.

Example Chrome-tanned sheep skins with considerable amounts of chrome soap deposits in the wool were first washed for l to 1 /2 hours at 40 to 50 C. in a solution containing 0.6 to 1 gm. per liter of a mixture of the sodium salts of monoesters formed by esterifying phosphoric acid with a fatty alcohol fraction having from 12 to 18 carbon atoms in the carbon chain and alkoxylated with 8 mole of ethylene oxide, and 0.5 gm. per liter of a sodium alkyl .18 carbon atoms. Finally, the skins were again rinsed with water at 40 to 50 C. Even when the furs were highly contaminated with chromesoaps, the above-described treatment produced pure white, clean wool on the sheep skins, which did not discolor.

. However, even if the fur has only relatively small amounts of chrome acid deposited thereon, it is in all cases advantageous to treat the furs, subsequent to chrome-tanning, with 0.3 to 0.6 gm. per liter of the washingagents according to this invention, if desired in combination with 0.3 to 0.5 gm. per liter of a customarily used washing agent, and with 1 to 1.5 gm. per liter of washing agent subsequent to an intermediate rinsing.

While we have given a specific embodiment of our invention, we wish to to be understood that various changes and modifications can be made therein without departing from the spirit of the invention or the scope of the appended claims.

We claim:

1. A process for Washing chrome soaps from the fur of chrome-tanned fur skins, said chrome soaps being derived from the natural fats on said fur skins and deposited on said skins during the chrome-tanning process, which comprises immersing said chrome-tanned fur skins in an aqueous solution, said solution being maintained at a temperature from about 40 C. to about 50 C., said solution having dissolved therein a tri-functional chrome complex forming compound selected from the group consisting of (1) water soluble monoesters produced from ethoxylated fatty alcohols having from 12 to 18 carbon atoms in the hydrocarbon chain and a polybasic acid selected from the group consisting of citric, tartaric and phosphoric acid, and sodium and ammonium salts of said esters; and (2) sulfonates and ethoxylates of polycarboxylic acids produced from unsaturated fatty acids having from 12 to 18 carbon atoms in the hydrocarbon chain reacted with maleic acid, and thereafter rinsing said fur skins with water, wherein said ethoxylated compounds contain from 5 to ethoxy groups in the molecule.

2. A process for washing chrome soaps from the fur of chrome-tanned fur skins, said chrome soaps being derived from the natural fats on said fur skins and deposited on said skins during the chrome-tanning process, which comprises immersing said chrome-tanned fur skins in an aqueous solution, said solution being maintained at a temperature from about 40 to about 50 C., said solution having dissolved therein a surface-active. compound, selected from the group consisting ofsodium and ammonium alkyl sulfates, alkyl sulfonates and alkyl benzene sulfonates wherein the alkyl radical contains from 12 to 18 carbon atoms, and .a tri-functional chrome complex forming compound selected from the group consisting of (1) water soluble monoesters produced from ethoxylated fatty alcohols having from 12 to 18 carbon atoms in the hydrocarbon chain and a polybasic acid selected from the group consisting of citric, tartaric and phosphoric acid, and sodium and ammoniumsalts of said esters; and (2) sulfonates and ethoxylates of polycarboxylic acids produced from unsaturated .fatty acids having from 12 to 18 carbon atoms in the hydrocarbon chain reacted with maleic acid, and thereafter rinsing said fur skins with water, wherein said ethoxylated compounds contain from 5 to 10 ethoxy groups in themolecule.

3. A process for the removal of chrome soaps from the fur of chrome-tanned fur skins, said chrome soaps being derived from the natural fats on said fur skins and deposited on said skins during the chrome-tanning process, which comprises washing said chrome-tanned fur skins in an aqueous solution having dissolved therein a water-soluble salt selected from the group conisting of sodium and ammonium salts of an ethoxylated fatty alcohol monoester of phosphoric acid, wherein the fatty alcohol radical contains from 12 to 18 carbon atoms in the carbon chain and said ester contains from 5 to 10 ethoxy groups, and therafter rinsing said fur skins with water.

4. A process for the removal of chrome soaps from the fur of chrome-tanned fur skins, said chrome soaps being derived from the natural fats on said fur skins and deposited on said skins during the chrome-tanning process, which comprises washing said chrome-tanned fur skins in an aqueous solution having dissolved therein a water-soluble salt selected from the group consisting of sodium and ammonium salts of an ethoxylated fatty alcohol monoester of phosphoric acid, wherein the alcohol fatty radical contains from 12 to 18 carbon atoms in the carbon chain and said ester contains from 5 to 10 ethoxy groups, and a water-soluble alkyl sulfate selected from the group consisting of sodium and ammonium alkyl sulfates, alkyl sulfonates and alkyl benzene sulfonates wherein the alkyl radical contains from 12 to 18 carbon atoms, and thereafter rinsing said fur skins with water.

5. A process for the removal of chrome soaps from the fur of chrome-tanned fur skins, said chrome soaps being derived from the natural fats on said fur skins and deposited on said skins during said chrome-tanning process, which comprises washing said chrome-tanned fur skins in an aqueous solution containing 0.6 to 3 gm. per liter of the water-soluble sodium salt of an ethoxylated fatty alcohol monoester of phosphoric acid, wherein the fatty alcohol radical contains from 12 to 18 carbon atoms in the carbon chain and from 5 to 10 ethylene oxide groups, and 0.2 to 1 gm. per liter of a water-soluble alkyl sulfate wherein the alkyl radical contains from 12 to 18 carbon atoms, at a temperature of from 40 to 50 C., said alkyl sulfate being selected from the group consisting of sodium and ammonium alkyl sulfates, and thereafter rinsing said fur skins with water.

References Cited in the file of this patent UNITED STATES PATENTS 1,930,910 Rohm Oct. 17, 1933 1,949,990 Brodersen et al. Mar. 6, 1934 2,086,867 Hall July 13, 1937 2,144,647 Burchill et a]. Jan. 24, 1939 2,692,180 Schmitt et al Oct. 19, 1954 OTHER REFERENCES pages 500-504.

Gard: American Dyestuff Reporter, December 21, 1953, pages 867-870.

Pankhurst: Jour. of the Internatl Soc. Leather Trades Chemists, December 1946, p. 355.

McLaren: Jour. of the Internatl Soc. Leather Trades Chemists, February 1947, p. 62. 

1. A PROCESS FOR WASHING CHROME SOAPS FROM THE FUR OF CHROME-TANNED FUR SKINS, SAID CHROME SOAPS BEING DERIVED FROM THE NATURAL FATS ON SAID FUR SKINS AND DEPOSITED ON SAID SKINS DURING THE CHROME-TANNING PROCESS, WHICH COMPRISES IMMERSING SAID CHROME-TANNED FUR SKINS IN AN AQUEOUS SOLUTION, SAID SOLUTION BEING MAINTAINED AT A TEMPERATURE FROM ABOUT 40*C. TO ABOUT 50*C., SAID SOLUTION HAVING DISSOLVED THEREIN A TRI-FUNCTIONAL CHROME COMPLEX FORMING COMPOUND SELECTED FROM THE GROUP CONSISTING OF (1) WATER SOLUBLE MONOESTERS PRODUCED FROM ETHOXYLATED FATTY ALCOHOLS HAVING FROM 12 TO 18 CARBON ATOMS IN THE HYDROCARBON CHAIN AND A POLYBASIC ACID SELECTED FROM THE GROUP CONSISTING OF CITRIC, TARTARIC AND PHOSPHORIC ACID, AND SODIUM AND AMMONIUM SALTS OF SAID ESTERS, AND (2) SULFONATES AND ETHOXYLATES OF POLYCARBOXYLIC ACIDS PRODUCED FROM UNSATURATED FATTY ACIDS HAVING FROM 12 TO 18 CARBON ATOMS IN THE HYDROCARBON CHAIN REACTED WITH MALEIC ACID, AND THEREAFTER RINSING SAID FUR SKINS WITH WATER, WHEREIN SAID ETHOXYLATED COMPOUNDS CONTAIN FROM 5 TO 10 ETHOXY GROUPS IN THE MOLECULE. 